Study attributes 60-70% of excess heart disease among low-income Americans to poverty rather than traditional risk factors

The COVID-19 epidemic has brought attention to longstanding health disparities in the United States. Heart disease, a key risk factor for severe COVID illness, is more widespread among lower-income Americans and may be a factor in the disproportionate effect of COVID-19 in low-income communities in the United States.

While some prior work has suggested that the higher rates of obesity, diabetes and tobacco use among the poor cause their added burden of heart disease, other studies point to additional upstream effects of being poor that directly increase heart disease risk.

According to a new UCSF study, traditional risk factors like hypertension, diabetes and smoking account for less than half of the excess burden of heart attacks and strokes among poorer Americans. Sixty percent of the excess is attributable directly to other aspects of living in poverty, according to a paper published today in JAMA Cardiology. Rita Hamad, MD, PhD, is the first author and Kirsten Bibbins-Domingo, PhD, MD, MAS, chair of the Department of Epidemiology and Biostatistics, is the senior author.

These findings challenge the current strategy for narrowing the gap in heart disease between economic haves and have-nots.

“We know as doctors that hypertension, for example, is more common in low-income communities,” said Hamad, an assistant professor of family and community medicine. “When we prescribe and monitor appropriate blood pressure medications for our lower-income patients, we might feel we’ve done what we can do. But this study shows that if we really want to improve the health of our patients, we have to integrate social services into health care, potentially intervening outside of the health care system to address poverty, low education, housing affordability and the stress of poverty itself.”

It’s not practical or ethical to run a decades-long clinical trial randomly assigning individuals to high- or low-income livelihoods. The researchers therefore leveraged the Cardiovascular Disease Policy Model, a well-established simulation tool developed at UCSF that integrates the best data on cardiovascular disease risk to simulate the entire U.S. population.

The team focused on premature heart disease with onset between the ages of 35 and 64. A quarter of the U.S. population in this age group – 31.2 million people – were low income, defined in the study as having income below 150% of the poverty line or less than a high school education. Using the Cardiovascular Disease Policy Model, the researchers waved a statistical magic wand, giving the low-income group the same established risk factors at the same rates as the higher-income group. In a second experiment, they completely erased all of those risk factors in the low-income group. They ran a 30-year simulation to examine the long-term impacts on cardiovascular disease.

They found that of the 1.3 million poor Americans who were 35 years old in 2015, 250,000 of them are likely to develop heart disease before they turn 65. That is almost twice the rate that would be anticipated in the higher-income group. Erasing the effects of traditional risk factors including smoking and obesity revealed that 70% of the excess burden of heart disease on this poorer cohort is due to poverty and its associated risks. In an analysis of Americans aged 35-64 right now, the same approach attributed 60% of the excess burden of heart disease to poverty.

Hamad said, “Our numbers reinforce the high toll poverty takes and the risk it poses for heart disease. We certainly need to address tobacco and hypertension, but we also just as clearly need to address poverty itself if we are to keep these communities healthy.”

The findings also have sobering implications for the COVID-19 pandemic.

“The same low-income groups who have higher risk of cardiovascular disease – which is a major risk factor for severe COVID-19 illness – are the people who are more exposed to the virus by virtue of living in dense urban areas and working in service jobs,” Bibbins-Domingo said. “The pandemic is calling attention to health disparities that have been simmering for a long time.”

The new study shows that social services must be a front-line tactic in efforts to narrow those gaps.